Method and apparatus for treating presbyopia

ABSTRACT

An apparatus and method are disclosed for treating near vision loss or deficiency, such as presbyopia. In contrast to conventional techniques, a peripheral ablation is provided in an annular zone of the cornea ranging from 5.5 to about 10+ mm to increase the dioptic power of this peripheral zone. The central zone disposed within the peripheral zone of the cornea is left untreated, is corrected for other vision deficiencies or is corrected so that it reverts to its characteristics prior to the peripheral ablation.

BACKGROUND OF THE INVENTION

[0001] A. Field of Invention

[0002] This invention pertains to a method and apparatus for treatingeye disorders associated with imperfections of a patient's eye and itsdisability to accommodate for near vision. More particularly, thepresent invention pertains to a method and apparatus for treatment ofpresbyopia by shaping an annular or extreme peripheral portion of thepatient's cornea to increase its refractive power, preferably usingautomated laser equipment.

[0003] B. Description of the Prior Art

[0004] Normally, a sharp image of an object is produced by a person'seye when the image is correctly projected on the retina. The process offocusing the image on the retina is referred to as accommodation, and itdescribes varying the curvature of the lens to change its focal point.More specifically, objects disposed at distances exceeding a certainthreshold (usually about 5 m) are seen clearly by a human eye with noaccommodation required and the eye is relaxed. For objects closer thanthis threshold, the eye must accommodate by squeezing the lens toincrease its thickness and change its focal point.

[0005] As a person gets older, the lens in his eye and its supportingstructure, such as the ligaments or zonules lose elasticity and heslowly loses his ability to accommodate. As a result he can no longersee close objects clearly, i.e., he suffers near vision deficiency. Thiscondition is known as presbyopia.

[0006] Until about ten years ago the conventional means of treatingpresbyopia was by use of positive lenses (in the form of eye glasses orcontact lenses). Persons who also had other problems, such as myopia orastigmatism, used negative and cylindrical lenses, respectively. Thesepeople had to wear bifocal glasses or contact lenses, i.e., lenses withat least two different portions: a superior portion with one curvatureand an inferior portion with another curvature. A person wearing thesekinds of lenses has to get used to looking at far objects through thesuperior portion and looking at close objects (in order of 40 cm orless) through the inferior portion. Eyeglasses are also known withlenses which change gradually from one portion to another so that thelenses have various zones, each zone being optimized for looking atobjects within a particular distance range.

[0007] Wearing bifocal or multifocal glasses has several disadvantages.One disadvantage is that some persons can get dizzy from such glassesand in fact they can never get used to them. These people normally havetwo kinds of glasses: one for near vision and another for distantvision. Another disadvantage is that many people find glassescosmetically unacceptable.

[0008] Contact lenses are generally more acceptable cosmetically thenglasses. However it is difficult to make bi- or multifocal contactlenses and so at present as presbyopia sets in, some people with contactlens must resort to glasses as well for near vision.

[0009] Recently, new techniques have been developed that use lasers tochange the optical characteristics of the cornea. Typically, thesemethods consist of reshaping the cornea by steepening portions thereof.Some methods and apparatus for performing laser surgery on the eyes aredisclosed for example in U.S. Pat. Nos. 5,350,373; 5,425,727 6,129,722and PCT Publication WO 00/27324 all incorporated herein by reference.All these reference disclose methods and apparatus for corrective eyesurgery, such as presbyopia, in which a laser beam is directed at thecornea and an ablation is performed to remove material from the corneathereby changing its optical transmission characteristics. Theseprocedures are performed using one of two techniques. The firsttechnique involves producing an ablation of the cornea in a central zonethereof. The central zone has a diameter in the range of 1.0-3.0 mm andthe ablation causes the central zone to steepen thereby increasing itsrefractive power. This technique is based on the underlying theory thatthe central zone of the eye is used for close vision while a peripheralzone of the cornea is used for distant vision. This theory is attributedto the fact that the pupil of the eye is closed by a sympathetic reflexwhen the person looks at objects located closer than 40 cm. According tothis theory, since the pupil opens or dilates for distant objects, theannular portion of the cornea must be used to see far objects.

[0010] In other words, some present laser surgical techniques are basedon a theory that categorizes the cornea into two zones: a central zoneof about 1.0-3.0 mm that is used for near vision (for objects up to 40cm); and an annular zone extending from 3.0 mm that is used for distantvision. Based on this theory, for each type of vision problem, the eyeof a person is corrected by ablating the appropriate zone withoutmodifying the other zone. More specifically, according to this theory,presbyopia is treated by steeping only the zone extending from 1.0 to 3mm of the cornea to augment the convergence power of this zone, therebyfocusing close objects onto the fovea.

[0011] According to the second theory the mulitfocality of the centralzone of the cornea is used to view objects at different distances.Accordingly, presbyopia can be corrected by partitioning the centralzone of the eye into several regions, ablating these regionsindependently to obtain different curvatures, each curvature defining adifferent dioptic powers for the respective region. The multifocalitythus obtained may be achieved by excimer laser ablation with tissuebeing removed from the central zone of the cornea at different depthsfor each optical region. A person can then use each of the regions tolook at objects at corresponding ranges including near vision.

OBJECTIVES AND SUMMARY OF THE INVENTION

[0012] In view of the above, it is an objective of the present inventionto provide a method and apparatus for treating eye disorders which aremore effective then conventional methods and techniques.

[0013] A further objective is to provide an improved method which doesnot require expensive or difficult modifications to the existing eyetreatment apparatus.

[0014] Yet a further objective is to provide an eye treating method andapparatus which can be adapted easily to treat different eye disordersusing the novel as well as conventional techniques.

[0015] Other objectives and advantages of the invention shall becomeapparent from the following description.

[0016] The inventors have discovered that contrary to the theoriesdescribed above, the central zone of the cornea defined as the pupillaryarea is used by the eye for distant vision while the peripheral zone ofthe cornea is used for near vision. More specifically, the inventorsbelieve that near vision is produced by light passing through an annularzone extending between 5-10 mm or more of the cornea, said annular zonebeing disposed concentrically around the pupil. The remaining centralzone of about 5.5 mm is used by the eye for distant vision.

[0017] Accordingly, the inventors believe that any corrective surgeryfor the treatment of near vision, such as presbyopia should be performedin this annular zone, increasing the light that passes through the pupiland improving the intermediate and near vision. The inventors furtherbelieve sometimes that during the treatment of the peripheral zone ofthe cornea for near vision, the optical characteristics of the centralzone of the cornea may also change. However, in patients who do notsuffer from poor distal vision, such a change is undesirable. Therefore,as a secondary procedure, after the peripheral zone is corrected fornear vision, the central zone or pupillary area is also corrected toneutralize any undesirable optical changes in the central portion of thecornea that may have occurred as a result of the peripheral ablation.

[0018] The amount of material removed from the cornea for ablation, theoptical characteristics of the patient may be considered. For example,for patients having a large pupil, steeper cornea or deeper anteriorchamber, less tissue resection is needed and the corneal periphery. Forolder patients, more tissue resection is needed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1A shows a plan view of a person's cornea indicating acentral zone thereof that is subjected to near vision treatment inaccordance with conventional techniques;

[0020]FIG. 1B shows a somewhat enlarged cross sectional profile of thecentral ablation performed by conventional techniques to treat a nearvision deficiency;

[0021]FIG. 2A shows a plan view of a person's cornea indicating anannular zone thereof that is subjected to near vision treatment inaccordance with the present invention;

[0022]FIG. 2B shows a somewhat enlarged cross sectional profile of theperipheral ablation for near vision treatment of the cornea performed inaccordance with the present invention;

[0023]FIG. 2C is similar to FIG. 2B but it also shows an additionalcentral ablation performed in accordance with the present invention;

[0024]FIG. 3 shows a block diagram for a laser apparatus used to providetreatment in accordance with this invention;

[0025]FIG. 4 shows a flow chart for the operation of the apparatus ofFIG. 3; and

[0026]FIG. 5 shows a cross sectional view of an eye with a cornea thathas undergone peripheral ablation in accordance with this invention.

DETAILED DESCRIPTION OF THE INVENTION

[0027] Referring first to FIG. 1A, as mentioned above, prior to thepresent invention it was believed that for near vision the eye makes useof light entering the cornea through a central zone b having a diameterof about 3 mm. Accordingly, most prior art techniques consist ofablating tissue at various depths in the cornea in a central zone bextending between 1 mm and about 3 mm. A small spot of about 1 mm is notablated. More importantly, the annular zone c extending from about 5 mmto 10+ mm is not substantially ablated during this treatment. FIG. 1Bshows a typical prior art profile resulting from central ablation. Ascan be seen in this profile, the central ablation is concentrated in thevicinity of the outer edge of zone b, i.e., at about 3 mm.

[0028] According to the present invention, the treatment should not beapplied to the central zone of the cornea but to its outer peripheralzone. FIG. 2A shows a schematic view of the cornea with a central zone Aof about 5.5 mm and an annular or peripheral zone B extending from 5.5mm to 10+ mm. A typical profile 100 resulting from peripheral ablationin this peripheral zone B is shown diagrammatically in FIG. 2B. Thisablation profile 100 is selected to steepen at least a portion of thisperipheral zone B and correct the near vision of the patient forpresbyopia and other near vision deficiencies. The size and shape ofthis ablation profile 100 is determined using standard techniques wellknown in the art and will not be discussed in detail, however in makingthe ablation the following patient characteristics are relevant:

[0029] A. The Pupillary Size.

[0030] An important advantage of the present invention is that a highrefractive power peripheral cornea is obtained that allows more light toenter through the pupil. Therefore the pupillary size of the patient isconsidered when deciding the depth of the peripheral ablation.

[0031] B. The Preoperative Corneal Curvature.

[0032] The flatter the cornea is the deeper the treatment is required inorder to achieve the desired level in which the peripheral power of thecornea corrects the presbyopia.

[0033] C. The Anterior Chamber Depth.

[0034] This amount of light entering through the pupil is also dependenton the distance between the pupil and the peripheral cornea, where theablation is performed. Therefore this distance is also be considered.

[0035] During peripheral ablation, the central zone A of the cornea isnot subjected to any substantial treatment. However, during peripheralablation, the optical characteristics of the central zone A may alsochange. Therefore, during, or preferably after the peripheral ablationresulting in profile 100, central ablation is applied to the centralzone A to restore the vision of the patient through this central zone towhat it was prior to the ablation profile 100. FIG. 2C shows the profile102 of the ablation applied to the central zone A. As discussed above,the inventors believe that this central zone A is responsible fordistant vision which may be normal in a patient with presbyopia.Alternatively, if the patient suffers from poor distant vision as well,and/or has other visual problems the ablation profile 102 may be shapedto correct these problems. It should be understood that in FIGS. 2B and2C the profiles 100 and 102 are shown schematically only to illustratethe approximate positions of these ablations and not necessarily theiractual shape or size.

[0036]FIG. 3 shows a block diagram for an apparatus 10 arranged andconstructed to perform the near vision treatment. The apparatus 10 maybe adapted to perform either LASIK or PRK type of surgery. The apparatus10 includes a laser beam generator 12 which generates a laser beam L.The laser beam generator 12 may be an excimer or a solid state lasergenerator.

[0037] The laser beam L can be a broad beam, a scanning beam or a flyingspot type beam and is directed by an optical network toward the eye E ofa patient. The network may be manually adjusted using a manual control14 to insure that the beam L is focused and directed properly on thecornea F.

[0038] The apparatus further includes a keyboard 16, an automatedcontrol 18 (which is preferably is a microprocessor-based control) and aprofile memory 20. The keyboard 16 is used to enter various informationabout the patient and the surgical operation that is to be performed.Based on this information and other parameters programmed into it, theautomated control selects an appropriate profile for the ablation to beperformed. In other word, the automated control 18 relies on software todirect the laser beam precisely and determine the movements required toobtain the correct ablation depth, the number of zones for ablation andthe diameter of ablation. A set of profiles for various vision problemsmay be stored in the profile memory 20 and the automated control 18 canaccess and retrieve these profiles as required. The automated controlalso operates the laser beam. The apparatus shown in FIG. 3 may beimplemented using laser equipment from Autonomous Technology, VISX (Star2 and Star 3), Laser Sight, Weavelight, Alegretto, Schwind, Bausch andLomb, Keracor and Meditech Aesculap.

[0039] The procedure for performing ablation on a specific patient usingthe apparatus of FIG. 3 is now described in conjunction with the flowchart of FIG. 4. In step 40, the patient is examined to determine hiscurrent eye condition. For example a 55-year old male was found to haveplano distant vision and presbyopia. Next, in step 42 it was determinedthat the treatment for patient's presbyopia required a +2.50 sphericaldiopter correction. As part of this determination, a complete optometricand ophthalmological examination is performed on the eye, includingmeasurement of the corneal curvature, pupillary size, anterior chamberdepth, topography map and ultrasound pachymetry. This information wasfed to the automated control 18 which then determined the correspondingablation profile required to generate the +2.5 spherical dioptercorrection. In step 44 the ablation process was initiated and theautomated control performed the necessary peripheral ablation on thecornea of the patient. Since the +2.5 diopter correction is ratherdrastic, in step 44 the peripheral ablation profile was performed in twophases. A peripheral ablation of +1.5 spherical diopters was performedin the optical zone B from 6.0 to 9.0 mm. Then a second peripheralablation of +1.50 diopters was performed in the optical zone B from 5.5to 9.0 mm. The peripheral ablations are performed on the stromal tissuesof the cornea.

[0040] As discussed above, a peripheral ablation of the cornea mayadversely affect the central zone of the cornea. Therefore, in step 46the optical characteristics of the eye are checked again. In step 48 adetermination is made as to whether a correction is necessary for thecentral zone. For the subject patient, such a correction was necessary.Therefore, the apparatus of FIG. 3 was used to perform a centralablation to restore the optical characteristics of the central zone A.More specifically, in step 50 a central ablation of 42 microns centeredon the pupil was performed. If the patient suffers from other visualimpairments, such as hyperopia, additional or other treatment may beapplied during this step 50.

[0041]FIG. 5 shows a cross sectional view of the eye with peripheralablation 100 positioned in a peripheral zone of the cornea in accordancewith the present invention.

[0042] In summary, using the method and apparatus described, a highrefractive power peripheral cornea is produced by ablating a peripheralzone of the cornea extending from about 5.5 up to 10 mm or more withoutsubstantially changing the refractive power of a central zone of thecornea. The ablation steepens this peripheral zone to augment itsdioptic power, thereby allowing the eye to focus on close objectswithout the use of a lens. During this process, the central zone of thecornea is not treated to insure that the distant vision remainsunchanged. Since the central zone is not touched during the peripheralablation required to treat presbyopia, it need not be covered orotherwise protected. After the peripheral ablation is completed, thecentral zone may be ablated in order to revert it to its characteristicsprior to the peripheral ablation.

[0043] Numerous modifications may be made to this invention withoutdeparting from its scope as defined in the appended claims.

We claim:
 1. A method for treating loss of near vision in a patientcomprising: form a peripheral zone in the cornea having a highrefractive power to provide corrected near vision for the patient. 2.The method of claim 1 wherein said peripheral zone is exceeds about 5.5mm.
 3. The method of claim 2 wherein said peripheral zone has a diameterof less than about 10 mm.
 4. The method of claim 1 wherein therefractive power of said peripheral zone is changed without changing therefractive power of a remaining central zone.
 5. The method of claim 4wherein said central zone has a diameter of about 5 mm.
 6. The method ofclaim 1 further comprising changing the refractive power of a centralzone of the cornea disposed concentrically within said peripheral zoneto revert said refractive power to its value before the formation ofsaid peripheral zone.
 7. The method of claim 1 further comprisingchanging the refractive power of a central zone of the cornea disposedconcentrically within said peripheral zone to treat said central zonefor vision loss other than near vision deficiency.
 8. A method oftreating presbyopia in a patient comprising: peripherally ablating aperipheral zone of the cornea, said peripheral zone extending from about5.5 to about 10 mm to form a high refractive power peripheral cornea tocorrect said presbyopia.
 9. The method of claim 8 further comprisingleaving a central portion of said cornea untreated to provide distantvision for the patient.
 10. The method of claim 8 wherein during saidperipheral ablation, the optical characteristics of a central zone ofsaid cornea used for distant vision are changed, further comprisingproviding treatment to said central portion to revert said centralportion so that its optical characteristics are similar to thecharacteristics prior to the peripheral ablation.
 11. The method ofclaim 8 further comprising changing the optical characteristics of acentral zone of the cornea to correct said central zone for visiondeficiencies other than near vision loss.
 12. The method of claim 11wherein said changing comprises performing ablation on said centralzone.
 13. A method of performing surgery on an eye with near visiondeficiency comprising: determining the characteristics of the opticalcharacteristics of the eye; determining a positive diopter correctionfor the eye; determining a peripheral ablation profile corresponding tosaid positive diopter correction; and performing a peripheral ablationon the cornea using said peripheral ablation profile while a centralportion of the cornea remains untreated.
 14. The method of claim 13further comprising treating said central portion after said peripheralablation.
 15. The method of claim 14 wherein said treating includescorrecting said central portion to revert said central portion tooptical characteristics similar to its characteristics prior to theperipheral ablation.
 16. The method of claim 14 wherein said eye suffersfrom other deficiencies further comprising treating said central portionto correct said other deficiencies.
 17. An apparatus for treating apatient's eye for near vision deficiency comprising: a laser beamgenerator; an optical network adapted to deliver a laser beam from saidlaser beam generator to the eye of the patient; and a controller coupledto said optical network and said laser beam generator and adapted toprovide a peripheral ablation on a peripheral portion of the cornea toincrease the dioptic power of said peripheral portion thereby correctingthe eye for the near vision deficiency.
 18. The apparatus of claim 17wherein said controller is adapted to deliver said peripheral zone ofthe cornea within an area between 5.5 and 10 mm.
 19. The apparatus ofclaim 17 wherein said controller is adapted to leave a central portionof the cornea untreated during said peripheral ablation.
 20. Theapparatus of claim 17 wherein said controller is further adapted toprovide a central ablation to said central zone after said peripheralablation.
 21. The apparatus of claim 20 wherein said controller isfurther adapted to provide said central ablation to restore said centralzone to its condition prior to said peripheral ablation.
 22. Theapparatus of claim 20 wherein said controller is further adapted toprovide central ablation to said central zone to provide treatment tocorrect a deficiency other than near vision deficiency.